The only thing that significantly impacted my weight over the years was a more restricted diet. Currently I do not eat food after 6 pm, and have almost cut 100% of fast food out of diet. (At worst BMI 34, now BMI 25.)
So I loved BJJ (did not hate it the same way I hated the gym), but I physically had a hard time with it post 30 years old. Caveat emptor, I should probably not be giving anyone health advice.